Embodiments of the present technology generally relate to digitized waveforms that are displayed on pixilated screens. Certain embodiments relate to systems and methods of displaying digitized waveforms on pixilated screens.
Cardiologists spend much of their time looking at waveforms to determine the activity of the heart. The waveform is an analog signal that does not contain discrete values, but instead is a record of smooth changes over time. To display this signal on a computer monitor requires interpreting these discrete values in such a manner as to display a continuous line on the screen. This is further complicated by the fact that the screen is itself broken into discrete points, called pixels.
Starting with discrete waveform values for each screen location, it is possible to “connect the dots” and draw lines that form a visual representation of the signal. The initial algorithm that was used for drawing lines on a digital screen, known as the Bresenham algorithm, creates one-pixel wide lines between two points using linear-interpolation using only integers. The general outline of this algorithm has been used in drawing signal waveforms for as long as computer-assisted cardiology has been in practice. This routine runs very quickly, so at a time when processor power was very limited, this method was the most appropriate. Drawing signals using this method causes aliasing, a visual stair-step effect, because the line actually passes halfway between the pixels that are available for display. To combat this, a number of techniques exist to anti-alias waveform lines during the drawing process. These methods generally involve modulating the color of various pixels used to form the line, and require more processing in order to produce improved results.
A traditional cardiogram was plotted by means of an inked stylus moving across a piece of paper that was being dragged at a constant rate. Consequently, the baseline of the signal was thicker than the rises or falls, due to the ink flow rate being constant, but velocity changing depending on the movement of the stylus. This produced a very characteristic look that the cardiologist could use to help interpret the waveform.
Present systems do not provide this characteristic look, and do not allow a user to customize waveform display settings to control waveform line thicknesses. Also, present anti-aliasing techniques can require excessive processing, and may not provide desired results.
Thus, there is a need for improved systems and methods for displaying digitized waveforms on pixilated screens.